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Help me understand rectifier behavior

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(@cecil)
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@davee  I do not know exactly what my load will be but the circuit designer recommends a 500 mA transformer and at least one person got it to work with a 200 mA transformer.  I ordered an 800 mA transformer so I think I'll have plenty of overhead.

I very much appreciate your theoretical explanation.  I'm sure I do not understand it thoroughly but I can follow it.  It makes me want to buy an oscilliscope.  I did buy one 15 years ago for $10 at an estate sale but it died after the screen came on for one second.  

Anyway, if I was starting over with what I learned from @zander'a link, I would power my project with a 20VAC 800 mA wall wart I already have.


   
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(@cecil)
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@zander  I know some of what you mean about border hassle.  I sold used goods to Canadians a few times.  I also once represented a client in a lawsuit against a car dealer who thought a test drive across the border and transfer of possession in Canada would protect him from US liability for misrepresentation.


   
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(@cecil)
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Correction:  It was @robotbuilder's link that lit a lightbulb for me.


   
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Inst-Tech
(@inst-tech)
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@zander One use for a milliOhmmeter is to measure current shunts. In instrumentation calibration, we often use  decade boxes to calibrate temperature transmitters using Platinum and copper RTD, and thermocouples..

FYI: this is a link to understand what they are , and how to use one..although I do 't think you'll probably ever need one...lol

https://wiki.analog.com/university/courses/tutorials/alm-milli-ohm-meter

As a process control tech, my back ground is metrology...

metrology
 

mĕ-trŏl′ə-jē

noun

  1. The science that deals with measurement.
  2. A system of measurement.
  3. The science of weights and measures.

Regards,

LouisR

LouisR


   
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Ron
 Ron
(@zander)
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@inst-tech Thanks for the explainer. I am a little bit familiar with the current shunts as I use one in my solar setup to count all the energy going into my battery and all the energy going out of my battery. The software and display (purchased) display how long the battery will run at the current load, what % full the battery is, and all the obvious power measurements and the temp at the most negative or positive post (I have one at each and do not recall which is which)

I was involved in a funny story involving a similar but opposite end of the spectrum device to your decade box. In high school, I got a summer job at Westinghouse switchgear, and one assignment was testing the new at the time constant current device. This device was 8 ft tall, 50 ft long, and 8 ft wide. It was full of meters and relays ranging in size from an average book to a small bar fridge. It kept blowing a transistor in the control circuitry, and when it did, we had to call the engineers down to have a look. Now Westinghouse was famous for importing engineers, many from the UK, hoping they would get trained on Westinghouse gear and then leave and, due to familiarity, recommend the products. Not because they were good! Many had a pipe, and all had leather patches on their elbows.  what usually happened is we would run the test and watch another transistor go up in smoke. The engineers would nod and mumble and point with their pipe stem before heading off to try and figure out what was wrong. I worked with my uncle, a practical electrician, and after they were gone, we brought over a cart of maybe 4' x 4' x 4' full of configurable wire resistors. We would hook it up, put it across the load set at max, and watch the wire resistors glow red. Then we slowly dropped the resistance until the transistor blew. We would note the current and resistance, put everything away, and wait for the engineers to return. When they did, we would tell them that we should put a resistor in the transistor collector (I think or emitter) to stop it from blowing because we didn't have that many spares. They thought that was a good idea so we would ask what value, and they shrugged their shoulders, so we would say well, we happen to have a few here; let's try this size.

This went on for some time to the great amusement of the hourly union labour types like my uncle and his co-workers before we finally got the right resistor. We never told those engineers how we figured it out. They probably think they had something to do with it. Typical for that bunch.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@davee)
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H @cecil,

  Hope some of my sermon made sense. Seeing it on a scope would be much clearer.

  It is worth noting that there are free simulators ... LTSpice is my usual first stop ... which have a 'virtual scope' built in. Using them is something of an art, that will take a while to acquire, but can also really help to 'visualise' how a circuit works. I amnot suggesting you immediately dash off in that direction, but it is a skill that is well worth 'bringing on board', and probably zero cost, if you ignore the increased coffee (or equivalent) consumption.

  I have only ever bought two 'new' scopes with 'my own real' money, with a gap of nearly half  a century, yet they cost a similar amount of money! Inflation works in reverse, so in 'real terms' they are so much cheaper than they used to be.. but sadly they are still not free!

  I confess I am not clear how your power supply requirements match up to your milliOhmeter design either, but as all electronics needs a power source, it is an important,and probably often neglected part of the total art. I hope you succeed in your total project.

Best wishes, Dave


   
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Ron
 Ron
(@zander)
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@cecil Specs say 0.001 at 5% accuracy, but I can't see ever needing that. Of course, it's from China, and I have no way of testing the claim, so it could be all hogwash.

I am fairly sure I paid less than $50 CDN

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@cecil)
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@zander   A Chineese commercial unit is only $75 and I am obviously going to more trouble than that since I have to build the device and its power supply.  Here's a picture of one ready-made and the schematic of what I want to build.

Your story about a semi-trailor size box of circuitry reminds me of a time in the seventies when I was present when a large steel warehouse received delivery of 512 kilobytes of memory for its mainframe.  It was the size of a refrigerator and took a fork lift to get it off the truck.  Times have changed.

CommercialMeter

 


   
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